What temp is "full spectrum"?

[pipspeak]

I see both 5000 and 6500K CFL bulbs being touted as "full spectrum" but which really is the most color accurate? I need a bulb for a work lamp that is able to render colors as closely as possible to daylight. Do I go for 6500 or 5000?

And is $3-4 a pop about right for a decent daylight CFL (75W equivalent) via an online retailer? Thanks.

 

[Ken_McE]

I see both 5000 and 6500K CFL bulbs

these will both be a touch on the cool side if you are used to incans, the 6,500 more so.

being touted as "full spectrum" but which really is the most color accurate?

In your situation what you need to look at is the "CRI" (color rendition Index) rating, not the color temperature. A low CRI means it is impossible to see colors. What you see when you walk around by moonlight would have a CRI rating of, oh, one maybe? A CRI of 100 is as high/perfect as the scale goes and I believe that full sunlight at noon is the standard reference for a CRI of 100. There are bulbs available that will get you into the nineties, but you will have to seek them out. They cost a little more so you won't find them just sitting around at the Home Depot.

I need a bulb for a work lamp that is able to render colors as closely as possible to daylight. Do I go for 6500 or 5000?

Between these two the 5,000 is better, but neither one of them is going to satisfy your requirements. I seem to recall that the CRI of an incan is not that bad, so you could pair one up with your CFL as a quick and dirty working solution. I believe that halogen bulbs may be good for color also. We have some old oil paintings that I got high CRI MR-16 bulbs for, if you want I can check the brand. They brought out details that I had never seen with the standard incan bulbs.

If you don't mind my asking, what is it you're looking at and what kind of fixtures/bulbs can you use?

*********************Added Comment***************

I have some bulbs by these people:

http://solux.net/comparisonindexpage.htm

they are MR-16 style incans of some sort, run off 12 V ac or dc. I picked them because they promised good color rendering with a sharp UV cutoff. They've performed as promised. You'd need an awful lot of them for a whole room but they'll light a painting very nicely.

There are also lamps by these people:

http://www.ottlite.com/

They make small high CRI fluorescent products. I have two of their lamps and they do provide good color rendering. I can't find a spectrum or CRI rating on their website, which is a bad sign, but maybe they're in there somewhere.

 

[SafetyBob]

1000bulbs.com usually carry "full spectrum" bulbs. But as stated above, there is some homework to do. I first put 6500K bulbs in the garage and it lit the place up but I recently went to a local electrical distributor and they had the 5000K variety and I think I prefer them over the 6500K now.

That CRI number is important. Pay close attention when purchasing bulbs for critical lighting area!

Bob E.

 

[65535]

I Personally Use 6500K bulbs in my room 4 foot T8 IIRC, 64 watts of 6500K lighting for me gives a plenty high CRI in the 80's I think, for the Highest CRI you are probably looking at 5500K color corrected bulbs, they aren't going to be cheap. They are what my moms office uses, she is in the housing color industry, so CRI counts definitely.

 

[jtr1962]

For most uses 5000K to 5500K is best. If you can go with T8 tubes you'll have lots more choices available than you do with CFLs. Also, the tubes are cheaper, last far longer, and are 50% more efficient. This place has all sorts of full-spectrum lamps. I'm using these tubes with good results. These look even better. I'll probably give them a try when my present tubes go. For what it's worth, it takes a trained eye to be able to tell the difference between "full-spectrum" tubes with CRI in the low 90s and commodity 5000K, CRI 86 tubes like these which are less than half the price.

I'd stay away from Ott-Lite. Their lamps are overpriced for what they are. Also, regular or halogen incandescent wouldn't be good for your uses. The color temperature is way too low. Blues, violets, and greens won't show up accurately. Color-corrected incandescent might work, but to me it doesn't even register on a list of options. It's horribly inefficient, creates a lot of waste heat/uses a lot of power for a given brightness level, and replacing dead lamps quickly becomes a chore. Best bet is to convert your fixtures to electronically-ballasted T8s, and purchase some full-spectrum tubes.